1. Field of the Invention
The field of the invention is devices that are placed on telephone lines to inhibit multiple instruments on the telephone line from interfering with each other.
2. Description of the Related Art
With the advent of so many different instruments which are adapted to attach to telephone lines, problems have developed with respect to interference between these different instruments when they are connected in parallel on a single telephone line. For example, it is common in business offices, and to some extent, in residential homes, to have multiple telephones on a single incoming telephone line or each to have access to the same telephone line, as well as other instruments, such as modems which permit attached computers to communicate with remote computers by sending and receiving data on the telephone line.
With the use of high speed modems, such as the 1200, 2400, or more baud modems, data is sent over telephone lines at an ever increasing rate. In order for the data to be free of distortions, it is preferable to have a single line dedicated to the computer. However, leasing a telephone line solely for a computer may be rather expensive so it has become common practice to use the common telephone line and to share it with the office telephones and other instruments.
However, results of using shared telephone lines by computers have resulted in distorted data being sent and received if a telephone or other device on the telephone line goes off-hook (receiver is picked up) during the time of data transmission. This injects electrical spikes and voltage fluctuations into the telephone line which distorts the data being sent and received by the modems resulting in error or, in some cases, even having the modems terminate transmission.
It is common in situations where different instruments are on a common telephone line to place mechanically operated switches, preferably near the computer, which switch the telephone lines to the computer modem and switch out all other parallel telephones or other instruments connected to the line. This type of operations works well and does reserve the telephone line pair for the computer while the switch is holding the telephone line in that position, however, it does create problems if the computer operator neglects to re-position the switch back to the telephones or other instruments on the line after computer transmission is completed. If the telephone line computer switch is located in another room from the party seeking to use a telephone after computer use, and the switch has been left in the computer position, this requires that the party desiring to use the telephone or other instrument travel to the switch and put it in the correct position. Further, if one party is using telephone without the knowledge of the second party, and the second party has access to the telephone line computer switch, the first party will be cut off as the switch is operated to the computer position.
In addition, other applications of the telephone line switch have been in commercial establishments, such as restaurants, where the proprietor has a public telephone on his business telephone line, and the proprietor makes the public telephone available whenever he is not using the line. If the telephone line switch is located near the proprietor's telephone, his forgetting to return the switch to the pay telephone line while his own telephone is not in use will result in lost revenues since the pay telephone is dead.
Obviously then, there is a need for a device which will, upon any instrument connected to the telephone line line going off-hook (being readied for use) to inhibit the operation of all other instruments similarly connected to that same telephone line in order that no other instruments on the line may interfere with the instrument being used, and which device returns the telephone line to use by any of the paralleled instruments on the line after use of the first instrument on the line.
This and other objects and needs are set out in the enclosed specification of the Applicant's invention.